1. Field of the Invention
This invention relates to an image forming device such as an LED printer, liquid crystal printer, laser printer or the like.
In this field, the printing operation of the printers mentioned above utilizes an electrophotographic recording system, and therefore, a printing operation giving high quality printed characters can be quietly carried out at a high speed.
2. Description of the Related Art
A direct current motor (DC motor) is usually used as a main motor for driving all the devices in the printer, including devices for carrying of the sheets.
The sheets are usually carried at a constant speed, and in a printing portion comprising an electrophotographic recording system, the writing of an image on a drum, referred to as a main scanning operation, is carried out in synchronization with the movement of the sheet. Accordingly, the DC motor is usually controlled at a constant speed and the rotational position of the DC motor is detected by a rotary encoder or the like, to synchronize the movement of the sheet and the writing of an image on a drum.
In the conventional system, however, since the DC motor is used as a main motor, and further since, the motor is controlled to a predetermined constant speed for synchronizing the writing of an image on a drum with the movement of the sheet, the size of the printer per se is large and the construction of the control circuit is complicated, thus increasing the production cost thereof.